Electronic throttle control apparatus for internal combustion engine

Abstract

An electric throttle control apparatus for an internal combustion engine includes a throttle motor that operates the throttle valve. A throttle control unit controls driving duty for operating the throttle motor. The throttle control unit determines a tapping operation for learning a full close position of the throttle valve to be completed when the accelerator position is at a substantially minimum position, the opening degree of the throttle valve is substantially constant in the vicinity of the full close position, and the driving duty for operating the throttle motor with respect to a close direction of the throttle valve becomes equal to or greater than a threshold. The throttle control unit restricts the driving duty to be equal to or less than a driving duty limiting value, thereby maintaining the throttle valve in the full close position, when the throttle control unit determines the completing condition to be satisfied.

1. An electric throttle control apparatus for an internal combustion engine, the throttle control apparatus comprising:
 a throttle valve; 
 a throttle motor that operates the throttle valve; and 
 a throttle control unit that controls driving duty for operating the throttle motor such that an actual opening degree of the throttle valve coincides with a target opening degree of the throttle valve, the target opening degree being set in accordance with an accelerator position, 
 wherein the throttle control unit is adapted for performing a tapping operation to learn a full close position of the throttle valve, 
 the throttle control unit determines that the tapping operation of the throttle valve is completed when the throttle control unit determines the following completing conditions to be satisfied: 
 the accelerator position is at a substantially minimum position; 
 the opening degree of the throttle valve is substantially constant in the vicinity of the full close position of the throttle valve; and 
 the driving duty for operating the throttle motor with respect to a close direction of the throttle valve becomes equal to or greater than a threshold, 
 wherein the throttle control unit restricts the driving duty with respect to the close direction to be equal to or less than a driving duty limiting value, thereby maintaining the throttle valve in the full close position, when the throttle control unit determines the completing condition to be satisfied. 
 
   
   
     2. The throttle control apparatus according to  claim 1 ,
 wherein the throttle control unit restricts the driving duty with respect to the close direction to be equal to or less than the driving duty limiting value when a predetermined time elapses after the throttle control unit determines the completing condition to be satisfied, and 
 the predetermined time is set within a maximum allowable period, in which 100% of the driving duty can be continuously applied to the throttle motor. 
 
   
   
     3. The throttle control apparatus according to  claim 1 , wherein the throttle control unit sets the driving duty limiting value in accordance with voltage of a power source of the throttle motor. 
   
   
     4. The throttle control apparatus according to  claim 1 ,
 wherein the driving duty limiting value includes a first duty limiting value and a second duty limiting value, 
 the throttle control unit individually sets the first duty limiting value and the second duty limiting value, 
 the first duty limiting value is used in the tapping operation, in which the throttle control unit learns the full close position by tapping the throttle valve at the full close position, and 
 the second duty limiting value is used after the tapping operation of the throttle valve is determined to be completed. 
 
   
   
     5. The throttle control apparatus according to  claim 4 , wherein the throttle control unit sets the second duty limiting value to be greater than the first duty limiting value. 
   
   
     6. The throttle control apparatus according to  claim 4 , wherein the throttle control unit sets the second duty limiting value to be less than the first duty limiting value. 
   
   
     7. The throttle control apparatus according to  claim 1 , wherein the actual opening degree of the throttle valve becomes substantially minimum in the full close position. 
   
   
     8. A method for controlling driving duty applied to a throttle motor operated using a throttle motor, the method comprising:
 performing a tapping operation to learn a full close position of the throttle valve, 
 determining the tapping operation to be completed when the following completing conditions are satisfied: 
 an accelerator position is at a substantially minimum position; 
 an opening degree of the throttle valve is substantially constant in the vicinity of the full close position of the throttle valve; and 
 the driving duty for operating the throttle motor with respect to a close direction of the throttle valve becomes equal to or greater than a threshold, 
 the method further comprising: 
 maintaining the throttle valve in the full close position by restricting the driving duty to be equal to or less than a driving duty limiting value, when the completing condition is satisfied. 
 
   
   
     9. The method according to  claim 8 , further comprising:
 setting a predetermined time within a maximum allowable period, in which 100% of the driving duty can be continuously applied to the throttle motor; and 
 restricting the driving duty with respect to the close direction to be equal to or less than the driving duty limiting value when the predetermined time elapses after the completing condition is satisfied. 
 
   
   
     10. The method according to  claim 8 , further comprising:
 setting the driving duty limiting value in accordance with voltage of a power source of the throttle motor. 
 
   
   
     11. The method according to  claim 8 , further comprising:
 setting a first duty limiting value of the driving duty limiting value and a second duty limiting value of the driving duty limiting value individually from each other; 
 maintaining the throttle valve in the full close position by restricting the driving duty with respect to the close direction to be equal to or less than the first duty limiting value in the tapping operation, in which the throttle control unit learns the full close position by tapping the throttle valve at the full close position; and 
 maintaining the throttle valve in the full close position by restricting the driving duty with respect to the close direction to be equal to or less than the second duty limiting value after the tapping operation. 
 
   
   
     12. The method according to  claim 11 , wherein the second duty limiting value is greater than the first duty limiting value. 
   
   
     13. The method according to  claim 11 , wherein the second duty limiting value is less than the first duty limiting value. 
   
   
     14. The method according to  claim 8 , further comprising:
 setting a target opening degree in accordance with an accelerator position; and 
 controlling driving duty for operating the throttle motor such that an actual opening degree of the throttle valve coincides with the target opening degree of the throttle valve. 
 
   
   
     15. The method according to  claim 8 , wherein the actual opening degree of the throttle valve is substantially minimum in the full close position.